Tagging a disk as SSD Disk in vSphere 6

There is a a very cool feature available in vSphere 6 which allows you to tag (mark) a devise as SSD/Flash device. Some time ESXi host do not recognize certain devices as flash when their vendors do not support automatic flash disk detection. The Drive Type column for the devices shows HDD as their type.

Why you need to do so?

Case 1: If you’re planning to deploy vSAN in your environment, then as a vSAN prerequisites you need some SSD disks (at least one per disk group).

Case 2: You want to use Host Cache Configuration feature so that host cache can be configured to use SSD drives and the virtual machine’s swapfile can be stored on this SSD drive for better performance as the SSD has much faster latency than a traditional mechanical disk Read More

Exporting/Importing vDS Configuration in vSphere 6

This will be a very short post on how to export vDS configuration from one vCenter and importing it in another vCenter. Lets get started.

If you have several vCenter server in your datacenter and you want to have a consistent and identical naming schemes for your distributed switch across all your vCenters, then you can save your time and efforts of creating vDS/Port groups on each vCenter manually by using the export configuration feature of vDS.

Login to vSphere Web Client and select the vDS (which is fully configured) and right click on it and select Settings > Export Configuration. Read More

Multipathing and Claim Rules

What is Multipathing?

Multipathing is having more than one path to storage devices from your server. At a given time more than one paths are used to connect to the LUN’s on storage device. It provides the ability to load-balance between paths when all paths are present and to handle failures of a path at any point between the server and the storage.

The vSphere host supports multipathing in order to maintain a constant connection between the server and the storage device, in case of failure that results in an outage of an HBA, fabric switch, storage controller, or Fibre Channel cable. Read More

VMFS Locking Mechanisms

In a shared storage environment, when multiple hosts access the same VMFS datastore, specific locking mechanisms are used. These locking mechanism prevent multiple hosts from concurrently writing to the metadata and ensure that no data corruption occurs. This type of locking is called distributed locking.

distributed lock.png

To counter the situation of Esxi host crashing, distributed locks are implemented as lease based. An Esxi host that holds lock on datastore has to renew the lease for the lock time and again and via this Esxi host lets the storage know that he is alive and kicking. If an Esxi host has not renewed the locking lease for some time, then it means that host is probably dead. Read More

Create,Configure and Manage Datastore Clusters

What is Datastore Cluster?

A datastore cluster is a collection of datastores with shared resources and a shared management interface. Datastore clusters are to datastores what clusters are to hosts.

When you add a datastore to a datastore cluster, the datastores resources become part of the datastore cluster’s resources. Datastore clusters are used to aggregate storage resources, which enables you to support resource allocation policies at the datastore cluster level. Also datastore cluster provides following benefits: Read More

Configure and Manage vSphere Flash Read Cache

What is vSphere Flash Read Cache aka vFlash?

Flash Read Cache helps in accelerating virtual machine performance through the use of flash devices residing in Esxi host as a cache.

vFlash was first introduced in vSphere 5.5. It allows you to use local SSD disks of Esxi host to create a caching layer for your virtual machines. By using host local SSD’s, you can offload some of the IO from your SAN storage to these local SSD disks.

vFlash aggregates local flash devices into a pool and this pool is called “Virtual flash resource” (vFRC). For example if you have 3 x 60 GB SSD you end up with a 180 GB virtual flash resource. Each local SSD configured for vFRC is formatted with a filesystem called VFFS  aka “Virtual Flash File System”. Read More

iSCSI Port Binding in vSphere 6

My first interaction with iSCSI and port binding was back in 2013 when we introduced an iSCSI based SAN (Dell MD3200i) in our environment. We were a small SMB entity and introduction of SAN for our vSphere environment was a very big thing for me as an administrator.

This was our architecture back then


I clearly remember that before starting the SAN implementation, I was contacted by Dell engineer to do some pre-work which included creating 2 vmkernel portgroup and each with only one vNIC as active and one as unused so as to achieve multipathing with iSCSI. Read More

VMFS Re-Signaturing

When you create a new datastore in vSphere, each VMFS volume is assigned a unique identifier (UUID) and this UUID info is stored in a metadata file as unique hexadecimal number.

You can see these UUID via ssh console of Esxi host.  In the /vmfs/volumes directory, each VMFS volume has a long string and a human readable names (which we configure from GUI while creating a datastore) as links to the UUID.


The UUID is comprised of four components. Lets understand this by taking example of one of the vmfs volume’s UUID : 591ac3ec-cc6af9a9-47c5-0050560346b9 Read More

My Notes on Raw Device Mapping (RDM)

Raw Device Mapping aka RDM is a way for providing virtual machine direct access to LUN on the SAN storage. The LUN presented to VM can be then formatted with any filesystem like NTFS or FAT for Windows OS and thus there is no need to format the LUN with VMFS filesystem and then place a vmdk on it.

RDM can be think of as a symbolic link from a VMFS volume to the Raw LUN. When an RDM is mapped to a virtual machine, a mapping file is created.This mapping file acts as a proxy for the physical device and contains metadata used for managing and redirecting access to the raw disk. Read More

Configure a virtual machine for Hot Add Features

VMware vSphere hot add is a feature that allows vSphere administrators to increase the RAM and CPU capacity of a running virtual machine on the fly. This feature is one of my favourites (second to vMotion). Hot add of CPU is usually referred as hot-plug, but I will be using term hot add for both RAM & CPU.

What so special about hot-add?

Think of older times when a physical server used to run out of resources (cpu/memory) and the administrator has to do shutdown the server to increase the capacity of server. Shutting down of server itself was a big headache in those time as the administrator has to get approval from the application owner, create a change request for maintenance etc etc. Read More

Virtual Machine Advance Configuration Options

When a virtual machine is created, there are number of files that are created alongwith. The most important among them is the .vmx file which is the configuration file of the VM. Whatever settings we chose during deployment of virtual machine, is written in this file along with many other configuration settings.

Although most of the virtual machine settings can be edited via web client, we can modify the vmx file directly (not recommended though) also to change configuration settings or to add some extra configuration items. Read More

Virtual Machine Disk Controller Configuration

In this post we will discuss about the different type of scsi controllers that are available with VMware vSphere and when to use which type of controller. We will discuss following topics in this post:

  • What is SCSI controller and their types
  • Why SCSI controller selection is so important
  • Storage Controller Compatibility
  • Adding/Changing SCSI controllers in virtual machines
  • Changing controller type by modifying virtual machine vmx file

so lets get started.

What is SCSI controller and their types?

SCSI controllers are used by virtual machine to access SCSI disks and other SCSI devices such as CD/DVD ROM. SCSI controllers are added automatically when a VM is deployed. Controllers can be added/modified also post creation of VM.

When a VM is created, the default controller that is assigned to it is optimized for best performance and the controller selection depends purely on the guest OS chosen at the time of VM creation. Read More

VUM orchestrated vSphere upgrades

VUM Orchestrated upgrades allow you to upgrade the objects in your vSphere inventory in a two-step process: host upgrades followed by virtual machine upgrades. If you want the upgrade process to be fully automated, you can configure it on cluster level or you can configure this at the individual host or virtual machine level for granular control.

Before going ahead with orchestrated upgrade, we have to ensure that we have baseline groups created for hosts as well as VM’s. I will talk more on this later in the post. Read More

Configuring vSphere Update Manager

In last post we learn how to configure UMDS and how to enable VUM to use shared repository for downloading patches. If you are new to VUM/UMDS and by mistake landed directly on this page, I would encourage reading about them first from below links:

1: Installing vSphere Update Manager and Update Manager Download Service

2: Configure Update Manager Download Service

Also in past I have written one blog post on Creating Esxi hosts baselines and how to remediate host. You can read that post from here. Read More

Configure Update Manager Download Service for VUM

Last year I wrote a post on how to install and configure VUM and UMDS, but never got chance to connect UMDS to VUM and ended up downloading patches directly on VUM server via internet.

Once again I am playing with UMDS in lab and in this post we will cover why we need UMDS and how to configure it.

I am not covering steps for installing VUM/UMDS here because they are pretty straight forward and if you are new to these things, you can read the instructions about installation steps from here.

What is Update Manager Download Service? Read More